1. Field of the Invention
The present invention relates to a ferromagnetic film, a method of manufacturing the same, and a magnetic head using the ferromagnetic film.
2. Description of the Related Art
A magnetic film for a magnetic head in the future is required to have a high saturation magnetic flux density Bs and soft magnetic characteristics (a low coercive force Hc and a low magnetostriction .lambda.s) so as to exhibit sufficient recording ability for a medium having a high coercive force.
Conventionally, an NiFe alloy film and a Sendust (FeAlSi)-based alloy film are known as crystalline magnetic films having good soft magnetic characteristics. However, the Bs of such a magnetic film is maximumly 15 kG. Many Fe- or Co-based alloys exhibit low Hc upon being changed into amorphous alloys. However, maximum Bs of an amorphous alloy film is also 15 kG.
The present inventor has paid attention to a CoFe-based alloy having high Bs of 19 kG or more throughout a wide composition range and made studies on a method of imparting soft magnetic characteristics to a CoFe-based alloy film. As a result, the present inventor reported that, when an fcc-phase (100) orientation is realized by a nitrogen-added sputtering method, a magnetic film having a comparatively low Hc of about 3 Oe and a low magnetostriction of +1.times.10.sup.-6 or less can be obtained (J. Appl. Phys., 67(9), pp. 5120-5122 (1990)). It is also reported that a CoFe alloy having similar Hc and a magnetostriction of substantially O is obtained by a plating method.
When an application to a magnetic head is taken into consideration, however, the Hc must be decreased to be about 1 Oe or less which is substantially equal to that of an NiFe alloy film, a Sendust film, or amorphous films.
Further, in a magnetic film formed of a CoFe-based alloy or Fe-based alloy containing, for example, Al as a third element, when the amount of the third element is reduced to improve saturation magnetic flux density, it is confirmed that the coercive force of an initially formed portion of the film is deteriorated, though the average coercive force of the entire film is low. Accordingly, if such a magnetic film is used in a metal-in-gap (MIG) head, the initially formed portion having a deteriorated coercive force may serve as a pseudo-magnetic gap, thereby generating a ripple in the frequency characteristic of the output of the head, so that good reproduction characteristics cannot be obtained.
On the other hand, in a magnetic film formed of a CoFe-based alloy containing a transition metal as a third element to serve to render the alloy amorphous, growth of crystal grains is caused due to the raise of the substrate temperature in the later stage of film formation by sputtering, resulting in a deterioration in the coercive force of the film.